Networks comprised of wireless sensor nodes are known in the art. A plurality of wireless sensors may be distributed throughout a building, for example, to monitor various environmental circumstances of interest (such as temperature, humidity, proximal human activity, noise, motion, and essentially any other sensable condition that might occur proximal to such a sensor). In many cases at least some of these wireless sensors comprise stand-alone platforms having only limited power, memory, and computational resources. Challenges often exist, therefore, to ensure useful application of such wireless sensors while also at least attempting to extend the useful operating life of the sensor platforms themselves.
Such platforms also often have a relatively limited transmission range. To illustrate, wireless sensors operating at 2.4 GHz and using IEEE 802.15.4 signaling protocols and in compliance with transmission power guidelines set forth by the United States Federal Communication Commission often have a maximum transmission range of only about 50 meters. To accommodate this situation many networks use a mesh-like solution to permit data to be moved upstream to a collection point via any number of intervening wireless sensors that essentially act as repeaters for downstream wireless sensors.
Many such wireless sensors comprise programmable platforms. This, in turn, permits re-programming and re-tasking of already deployed wireless sensor nodes (sometimes on a relatively regular and frequent basis). In many cases, however, such reprogramming will encompass all wireless sensors as comprise a given network. This, in turn, will typically result in each re-programmed wireless sensor acting in accordance with the newly deployed tasks and behaviors.
Unfortunately, such an approach tends to increase the number of computational and/or transmission events that a given wireless sensor must support and will also typically increase the amount of total time that such a wireless sensor must remain in an active operational state. Such operational circumstances tend to accelerate power usage and hence contribute, sometimes greatly, to diminishing the operational lifetime of a given deployed wireless sensor. This, of course, can be viewed in some cases as the inevitable cost of fielding and operating such a network.
In many cases, however, it is not necessary that all of the wireless sensor nodes as comprise a given network must or should actually act to implement such re-programming. In some cases a given wireless sensor node may not possess the requisite facilities that are necessary to accomplish a given task (for example, a given wireless sensor node may lack a temperature sensor and thus may not be able to effect a temperature measurement task). In some networks such information regarding individual platform capabilities is known and can be leveraged to permit more targeted provisioning of new programming.
In other cases, however, such information may not be known. Furthermore, in many cases the task in question may be best served by wireless sensors that have been fielded in a particular way. As a simple example, when a network includes some wireless sensors that are deployed while exposed to sunlight while others are deployed in permanently shaded areas, this circumstance can be of obvious importance when implementing tasks that require that the wireless sensor be exposed to sunlight. In such a case the re-programming and re-tasking of shaded wireless sensors will generate a waste of resources.
In yet other cases an inordinate amount of redundant task support may result. For example, four wireless sensors may all be capable of supporting a given task and may also all be sufficiently close to one another that each is essentially sensing a same ambient condition. As a result, having all four such wireless sensors re-program themselves and then act in accordance with that new programming can serve to deplete, without good reason, their limited resources.